1. Field of the Invention
This invention relates in general to segmented nuts for threaded shafts, and in particular a top connector assembly for connecting the upper end of a tendon to an offshore drilling production platform.
2. Description of the Prior Art
A tension leg platform is a type of offshore drilling structure. The platform floats and is secured to the sea floor by tendons. The tendons are large pipes, about 20-45 inches in diameter. After securing the tendons to the platform and to the sea floor, ballast water is pumped out to cause the platform to rise. The upward movement is resisted by the tendons, placing the tendons under tension load. The tendons under tension provide a stable platform for drilling and production.
U.S. Pat. No. 4,871,282, Charles E. Jennings, Oct. 3, 1989, U.S. Pat. No. 5,020,942, Joseph W. Pallini, Jr., Jun. 4, 1991; and U.S. Pat. No. 5,244,313, Joseph W. Pallini, Jr., et al., Sep. 4, 1993, describe top connectors for connecting the tops of the tendons to the platform. In the devices shown in these patents, the upper end of the tendon has helical threads. The threaded section extends through a housing which has conical bore or bowl. Segments or slips will slide down the conical bore from a retracted position to an engaged position. The segments have mating threads which will engage the threads on the tendon. A cam ring causes the downward movement of the segments and also rotates the segments and meshes the threads of the segments with the threads of the tendons.
The top connectors may be in a position exposed to sea water. It is desirable to protect the threaded areas from sea water. In the past, silicone rubber has been injected in the annulus between the housing and the shaft. Once cured, the silicone rubber provided the necessary low pressure protection of a seal, however the installation requires the use of a specialized curing agent and the use of divers. The silicone rubber also has a short pot life after mixing and requires equipment for mixing and injecting, as well as the cleaning of this equipment after injection.